A Novel Actuating–Sensing Bone Conduction-Based System for Active Hand Pose Sensing and Material Densities Evaluation Through Hand Touch

We realized and tested a novel system aimed at discriminating different hand poses by means of an active actuating and sensing approach realized by converting electromagnetic to mechanical waves (and vice versa) and analyzing the characteristics of the waves after their travel through the bones and cartilage of the hand. The actuating part is realized through a transducer, placed on the dorsal part of the hand, performing electromagnetic-to-mechanical energy conversion. The sensing part is realized through an accelerometer, placed on a finger, performing mechanical-to-electromagnetic energy conversion. The way the sound propagates through the fingers mainly depends on the traveled path, the angles of fingers' flexion, and the (un)matched conditions with surroundings. Therefore, the investigation of the characteristics of the returned signal (in phase shifts and power spectral densities) can furnish information for discriminating among different finger poses and different densities of touched materials. The system highly performed in repeatability and reproducibility of the measures, well-discriminating among hand poses and among densities of touched materials.